Electric furnace-control apparatus.



A. D. KEENE.

ELECTRIC FURNACE CONTRL APPARATUS.

APPLICATIGN FILED SEPT. 5. mi?.

Patente Feb5 5, i918,

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A n T hventow: Mivn I). Keene,

` UNITED sTATEs PATENT oEErcE.

ALVIN D. KEENE, OF SCHENECTADY, NEW YORK, ASSIGNOR 'IO GENERAL EL'TCTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE-CONTROL APPARATUS.

Specication of Letters Patent.

i Patented Feb;^5,'1918.

Application led September 5, 191'7. lSerial N o. 189,870.

To all whom t may concern.'

Be it known that I, ALVIN D. KEENE, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful4 Improvements in Electric Furnace-Control Apparatus, of which the following is a` specification.

The present invention relates to electric control apparatus for electric furnaces, particularly for arc furnaces. 'The object of my invention is to provide means whereby the electrodes may be automatically moved into contact with a stationary conductorat the beginningof the furnace operationv to strike the arcs, and to enable the setting of the control apparatus to be changed coincidentally with a change in connections of the energy supply circuit. I

The vnovel features of my invention willbe pointedfout with greater particularity in the appended claims and described in 4detail in the following description taken in connection with the'accompanying drawing which is a diagram illustrating my inven tion.

Referring to the drawing, the furnace is idiagrammatically indicated by a rectangle 1 shown in dotted outline, and comprises a stationary conductor or electrode 2 located at the base of the furnace, and movable electrodes 3, 3 adapted to support arcs in -series` in conjunction with the` stationary electrode 2. These electrodes may either all consist of carbon or graphite, or 1n some cases, the conductor 2 may be a charge of metal or other conductive material in thefurnace. A motor 4- is ymechanically connected to the electrode 3 by any form of suitable gearing, the drawing showing a speed reducing gear5 driven by the motor acting on a nut 6 on the screw-threaded rod 7 to raise and lower the electrode.

shown. The electrode is shown as connected to a Agearing 8 and it is to be understood that this gearing is connected to a motor and l vThe motor f connected to the` electrode 3 has not -been lower the electrodes in order to maintain the current in an are between the electrodes 3 and 2 substantially constant. The winding of a second contactor 2O is connected respec' tively to the conductor 10, which supplies the electrode 3 and to a conductor 21 which is connected to the electrode 2, thus being responsive to voltage variations of an arc operating between the electrodes 2 and 3.

The armature 2:2 of the contactor 20 is connected to a switch lever 23, adapted to contact with either of the conductors 24 or Q5 connected to a set of relays and contactors controlling the motor (not shown) for moving the electrode 3.

By this system of control one series arc being controlled by current variations and a second series arc by voltage variations, uniformity and regularity of arc length and vvoltage of the energy `supply may be changed. In circuit with the conductorQl is a fixed resistance 29 and a variable resistance 30. When the switch 28 is moved to'make contact with the conductor 31, thus completing the circuit of the supply conductors 3Q, then the switch 33, mechanically linked to the switch Q8, completes a shuntcircuit 31 about the resistance 29 and thus automatically sets the voltage contactor 20 to operate at a lower range of voltage than'is the case when the switch is moved to contact with the tap 35. thereby cutting out the section 27 of the primary winding.

Vlien the furnace is energized the contactor 36 pulls up its armature and causes the switch lever 36a to complete a circuit .between the conductors 37 and 38. ,In case the energy supplyis interrupted the contactor 36 releases and opens the circuit to safeguard the apparatus against injury.

The armature of the current-responsive 1 magnet 12 is in position to complete a circuit from the conductors 39, which are preferably supplied with direct current. To energize the relay magnet 19, the circuit being through the conductbrs 37, 38, lswitch lcvervl, conductors 16 an 41. The magnet 19 pulls up its armature 4s, closes contacts 43 and 44, and energizes the motor 4, the circuit being through the' conductors 45, resistance 46, contact 43, conductor 47, the armature of the motor, conductor 48, contact 44, and the conductor 41. The'motor is connected to thereupon lower the electrode 3 into contact with the conductor 2. A suitable circuit, for example, a resistance 40, connected across the gap between the electrodes 2 and 3, permits the voltage-responsive con tactor 2O to be energized and sets into operation a motor to lower the electrode 3', the control apparatus being like the apparatus energized by the current-responsive con-- tactor 12.

lVhen contact of both electrodes 3 and 3 is established, the electrodes are immediately raised again tostrike the arcs. In case of the current-responsive cont-actor 12, the lever 15 leaves the conductor 16, denergizing the magnet 19 and opening the contacts 43 and 44. 'The counter-electromotive force of the motor 4 energizes a contactor magnet49 connected across the conductors 47, 48, and by the closure of the contact 50, assisted by the spring 51, inserts a resistance 52 in the armature circuit to quickly bring the motor to rest by tor circuit is closed through the resistance 52, a mechanical interlock 54 prevents the closure of the relay magnets 18 and 19, which are attached respectiiely to interlocks 55 and 56. Upon .a iow ot' current, the contactor lever 15 completes a circuit through the magnet 18, through theconductors 37, 38, 17, 53 and 41. Before the magnet 18 may pull up its armature, the motor must come to a stop and release the mechanical interlocks 54,55. The same is true upon the reverse operation, the interlock 56 preventing closure of the contacts of the magnet- 19 until the motor comes to a stop. lVhen the motor is brought to rest, the relay magnet 18 closes the contacts 57, 58, and energizes the motor to raise the electrode 3, circuit being completed through the concluetors 41, 53, Contact 57, conductors 59, 47, the motor armature, conductor 48, contact 58, conductor 60, resistances 61 and 46, and the conductor 45.

Having described the operation of the relay mechanism for the current contactor 12, it will beI understood vwithout further de tailed explanation how the voltage contactor dynamic braking. yWhile the mo the operates to lower and raise the electrode 3 so as to maintairn an arc 5t predetermined length. The current of this second arc must necessarily be the'saine as the current'of the arc between the electrodes 3 rind 2 as the two arcs are electrically in series.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An electric furnace 'control apparatus comprising a plurality of electrodes, an electrical circuit connecting said electrodes to operate a plurality of arcs in series, means for controlling one of said arcs in response to variations of the current in said circuit, an electrical connection in shunt to said current-controlled arc and means for controlling another arc in response to voltage variations thereof.

2. An electric furnace equipment compris ing arc-supporting electrodes, motors operatively connected thereto, a source of electriclenergy, supply conductors connecting said source and said electrodes, means forl controlling said motors in response to electrical variations in said electrode circuits, means for changing the voltage of thelen'ergy supply, and means for automatically changing coincident therewith the setting of said motor control means.

3. The combination of an electric furnace. having a stationary electrode, a plurality of movable electrodes adapted to be maintained in arcing relation to said stationary electrode, series supply circuit connections to said movable electrodes, motors operatively connected to each of said respective electrodes, a resistance connected across one of said movable electrodes and said stationary electrode, means for controlling the motor connected to said last mentioned movablev electrode in response to current variations in the. supply circuit of said electrode, and means for controlling another movable electrode in response to voltage variations across said other movable electrode and said stationary electrode.

4. An electric furnace equipment comprising arc-supporting electrodes, electric motors operatively connected thereto, a source of electric energy, supply conductors connecting said source and said electrodes, a contactor connected to control one of said motors in response to the variations of the .current in the respective electrode circuit, a

second contactor connected to control a second motor in response to tariations of potential of an are supported thereby, means for changing the voltage oi said energy supply source, and means for automatically changing the setting of said contactors when the voltage of said supply source is changed.

5. An electric furnace equipment comprising a stationary electrode, tivo movable elec trodes 'cooperating therewith to operate two arcs electrically in series, a transformer for ion Anace conductor,

supplying electric energy to said electrodes to maintain said arcs, connections for changing the ratio of transformation in said transformer to change the secondary voltave ereof, means for adjusting said movab e electrodes with respect to said stationary electrode to maintain said ares of uniform length, vand means for automatically changing the setting of said adjusting means When changing the connections of said supplyA transformer. v

6. An electric furnace apparatus comprising two movable electrodes,a stationary furan electrical circuit for said electrodes for operating a plurality of arcs` the current in said circuit, a resistance in shunt to the :irc from said current-controlled electrode, and motor-operated means for adjusting the second electrode in response tov Voltage variations in said circuit.

In Witness whereof, I have hereunto set 25 ALVIN D. KEENE.

my hand this 4th day of September 

